A World to Explore

Archive for May 29th, 2011

MITZPE RAMON, ISRAEL–Today Will and I drove south, east and north to meet Dr. Yael Edelmen-Furstenburg of the Geological Survey of Israel. She gave us a most excellent tour of the Mishash (pronounced ME-shawsh) Formation (Campanian, Upper Cretaceous) in the Wadi Ashosh region (shown above) near Zuqim and Tsofar in the Negev Desert. We talked much about the fossil fauna, particularly the trace fossils in soft and hard substrates. There could be many future Wooster Independent Study projects in this formation, especially here where it is so diverse.

As seen above, much of the Mishash Formation consists of bands of chert. The folds are syndepositional (formed at the time of deposition) as part of the Syrian Arc deformation. This makes for some very interesting local stratigraphy and depositonal patterns.

The Mishash Formation has exquisite fossil shell beds, often silicified (replaced with silica). Above you can see gastropods and bivalves.

An old Cretaceous friend, the ammonite Baculites, is used to sort out the biostratigraphy of the Mishash. They are identified by the style of ribs they have on the outside of the conch.

Like everywhere else in the Negev Desert, shade is a bonus. We always appreciate the acacia trees, even if their shade is not so complete. Will is standing here next to the Geological Survey of Israel vehicle. Shlomo, an old friend and the driver, gave us quite the off-road adventure. Many people pay for such tours!

The sharp little conical fossils above are common Paleozoic fossils, especially in the Devonian. They are tentaculitids now most commonly placed in the Class Tentaculitoidea Ljashenko 1957. Tentaculitids appeared in the Ordovician and disappeared sometime around the end of the Carboniferous and beginning of the Permian. These specimens are from the Devonian of Maryland.

The systematic placement of the tentaculitids has been controversial. Their straight, narrow shells are usually ornamented by concentric rings, and many had septa (thin shelly partitions) inside the cones. The microstructure of the shells is most interesting — it looks very much like that of brachiopods and bryozoans. For this reason and several others, several of my colleagues and I believe the tentaculitids were lophophorates (animals that filter-feed with a tentacular device called a lophophore). They may thus be related to other problematic tubeworms like microconchids and cornulitids (Taylor et al., 2010).

Tentaculitids from the New Creek Limestone (Lochkovian, Early Devonian) of New Creek, West Virginia.

Knowing how the tentaculitids fit into an evolutionary scheme, though, has not helped us figure out what they did for a living. The figure below, from Cornell et al. (2003), shows these funny cones in just about every lifestyle imaginable!

References:

Cornell, S.R., Brett, C.E. and Sumrall, C.D. 2003. Paleoecology and taphonomy of an edrioasteroid-dominated hardground association from tentaculitid limestones in the Early Devonian of New York: A Paleozoic rocky peritidal community. Palaios 18: 212-224.